Friction shoe with damping for a railway car truck

ABSTRACT

A rail vehicle with two sideframes and a bolster as the freight car truck has limits on stability. A railway freight car truck having a friction shoe with a constant force device acting directly on the shoe flat surface is provided, such that the friction shoe is forced to remain in contact with the side frame mating vertical surface. The control spring acting on the friction shoe which applies a varying force to the side frame mating surface. The damping of the friction shoe is retained when there is less variable force of friction, which decreases vertical acceleration of the rail vehicle, providing high speed stability for most track conditions.

BACKGROUND

The traditional three piece railway freight truck consists of onebolster and two side frames. The side frames are supported at the endsby the wheelsets. The bolster which carries the car body extendscentrally through the side frames. The bolster is supported onsuspension springs. Suspension damping is created by friction shoeslocated between the side frame column vertical wear surfaces and angledpocket surfaces in the bolster. The suspension contains load springsthat support the bolster and control springs that support the frictionshoes. The friction shoes angled surfaces bear against the bolsterpocket having mating angled surfaces. The result of the control springforce acting on friction shoe against the angled support of the bolsteris a wedge force acting on the side frame vertical wear surface. Dampingis created by the wedge force of the friction shoe vertical surface andthe side frame vertical wear surface creates sliding force resistance tomovement. The friction shoe sliding force resistance increases as thecontrol springs are compressed. The sliding force resistance reduces thevertical acceleration of the car mass, which allows the railway freightcar to be stable for most track perturbations.

When the rail vehicle encounters vertical track perturbations thataccelerate the traditional three piece railway freight truck suspensionso there is limited compression of the control springs against thefriction shoes, little sliding force resistance occurs and the railvehicle vertical velocity increases. The force of friction is diminishedwhen the friction shoe sliding velocity increases to the point that thefriction shoe flat surface has low contact force to the side framesmating flat surface. This is due to a large difference in shoe flatsurface material static to dynamic friction coefficient. The frictionshoe is static till there is sufficient force to overcome the staticfriction. The large difference between static and dynamic frictionallows the shoe to accelerate with such force there is little to nodynamic damping. The materials surface roughness, uneven force impartedon the shoe, and the structure vibration add to the low damping of thefriction shoe. Once these conditions occur the control spring force uponthe friction shoe is not sufficient and the vertical accelerationbecomes excessive and the rail vehicle stability is reduced.

SUMMARY

The present friction damping arrangement stabilizes the friction shoewith a constant force device adjacent to and acting directly on the shoevertical surface, such that it forces the friction shoe to remain incontact with the side frame mating surface creating resistance tosliding by constant damping. When variable damping is diminished,constant damping of the friction shoes is retained, which decreasesvertical acceleration of the railway freight car, providing stabilityfor most track conditions.

The present friction damping arrangement balances the constant forcedevice with sufficient force acting directly on the friction shoevertical surface material such that the low static to dynamic frictioncan be used. Since the dynamic friction is retained the railway freightcar vertical velocity is reduced.

The present invention constant force device provides force through thebolster acting on the friction shoe vertical surface in turn acting onthe side frame vertical wear surface. The force between the side framesand bolster is sufficient to prevent warping or parallelogram movementof the railway freight car truck wheel set and bolster in relationshipto the side frames. The added force to prevent warping, increases thestability of the three piece railway freight car truck.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 is a perspective view of a railway freight car truck assembly inaccordance with first embodiment of the present invention;

FIG. 2 is a partial cut away view of a railway freight car trucksuspension in accordance with a first embodiment of the presentinvention;

FIG. 3 is a partial exploded view of a bolster and friction shoes of arailway freight car truck in accordance with a first embodiment of thepresent invention;

FIG. 4 is partial cut away view of the bolster end and friction shoes ofa railway freight car truck in accordance with a first embodiment of thepresent invention;

FIG. 5 is a detailed partial cross sectional view of the bolster end andfriction shoes with the cam per load device of a railway freight cartruck in accordance with a first embodiment of the present invention.

DETAILED DESCRIPTION

Referring now to FIG. 1, is a perspective view of a three piece railwayfreight car truck assembly 1 is seen to be comprised of two laterallyspaced side frames 7 between which bolster 8 extends. Bolster 8 is seento include bolster ends 11, which extend through side frame 7 openings14. Suspension springs 13 support bolster end 11 as well as frictionshoes 12. Friction shoes 12 provide vertical damping in the form ofsliding resistance between the side frames 7 and bolster 8. Bolster 8 isseen to include on its upper surface a bolster center bowl 10, and apair of laterally spaced side bearings 9. Wheelset 5 consist of twowheels 2 pressed on an axle 3. Wheelset 5 has axle roller bearings 4mounted at both ends of axle 3. The wheelset 5 bearings 4 support theside frames 7 on bearing connectors 6.

Referring now to FIG. 2, is a detailed cut away view of a traditionalthree piece railway freight truck suspension is shown with detailedpartial views of bolster 8 and side frame 7 in partial section. Bolsterends 11 extend through side frame opening 14 which are supported bysuspension springs 13. Suspension springs 13 consist of load springs 18which support the bolster 8 and rail vehicle. Suspension springs 13 alsoinclude the control springs 17 that support friction shoes 12 that havea sloped surface bearing against a complementary sloped surface formingbolster angular pocket 20. The suspension springs 13 are compressed bythe rail vehicle weight, lading, and track perturbations that occur whenthe rail vehicle is in transit. Damping is the result of the wedge forceon the friction shoe 12 flat surface 22 resistance to sliding againstand along the wear plate 16 of the side frame 7. The control spring 17compression and force varies depending on the vehicle weight, lading andtrack perturbations that displace the rail vehicle vertically duringtransit. Variable damping is the result of the control spring 17 varyingcompression and force. The lateral springs 15 bear against the centerrib 19 and place a constant force directly into shoes 12 thatsimultaneously direct the force to friction shoe 12 flat surface 22,which resists the sliding against and along vertical wear plate 16 ofthe side frame 7. The lateral springs 15 provide compression and forcethat are constant; therefore constant damping occurs.

Referring now to FIG. 3 a partial exploded view of bolster 8 andfriction shoes 12 is shown. Friction shoe 12 is cast of steel or iron.The friction shoe 12 has a recessed surface 22 to hold the friction shoeinsert 29. The friction shoe insert 29 is a composite or metallicmaterial. The friction shoe 12 on its angled surface 21 has recesses 23to retain lateral springs 15. The lateral springs 15 protrude throughapertures 24 in the bolster angled pockets 20. The lateral springs 15are preloaded and retained by cam 25 that are inserted through thebolster end 11 retaining holes 27 and the friction shoe 12 retainingholes 28. The cam 25 has a socket 26 on the end. Cam 25 with socket 26are used to preload lateral springs 15.

Referring now to FIG. 4 is detailed cut away of the bolster end 11 andfriction shoes 12 with the cam 25 per load device. The lateral springs15 are preloaded and retained by cam 25 that is inserted through thebolster end 11 retaining holes 27 and the friction shoe 12 retainingholes 28. The cam 25 has a socket 26 on the end. Once the cam 25 is inplace, it can be turned 90 degrees in retaining holes 27 and thefriction shoe 12 retaining holes 28. The rotation of 90 degrees extendcam 25 against friction shoe 12 which in turn compress lateral springs15. Once the bolster 8 is assembled into the side frames 7, the cam 25with socket 26 can be turned 90 degrees and the lateral springs 15 willapply a constant force on friction shoe 12.

Referring now to FIG. 5 is a section of the bolster end 11 and frictionshoes 12 with the cam 25 per load device. The lateral springs 15 arepreloaded and retained by cam 25 that is inserted through the bolsterend 11 retaining holes 27 and the friction shoe 12 retaining holes 28.The cam 25 has a socket 26 on the end. Once the cam 25 is in place, itcan be turned 90 degrees in retaining holes 27 and the friction shoe 12retaining holes 28. The rotation of 90 degrees extend cam 25 againstfriction shoe 12 which in turn compress lateral springs 15. Once thebolster 8 is assembled into the side frames 7, the cam 25 with socket 26can be turned 90 degrees and the lateral springs 15 will apply aconstant force on friction shoe 12.

What is claimed is:
 1. A railway car truck comprising a sideframe havinga substantially upright column partially defining a center opening, abolster having an end supported in the sideframe center opening forvertical movement therein, a vertical surface on the sideframe column,and a first wear plate attached to the vertical surface on the sideframecolumn, sloped surfaces on the bolster, a friction shoe comprising asubstantially vertical surface and a sloped surface extending at anacute angle with the vertical surface, a vertical spring urging thefriction shoe sloped surface into engagement with the first wear plateon the sideframe column and with the sloped surface of the bolster, anda horizontal spring urging the friction shoe vertical surface intoengagement with the first wear plate on the sideframe column.
 2. Therailway truck of claim 1 wherein the horizontal spring provides aconstant lateral force urging the friction shoe vertical surface intoengagement with the first wear plate on the sideframe column.
 3. Therailway truck of claim 1 wherein the vertical spring provides a variableforce urging the friction shoe sloped surface into engagement with thesloped surface of the bolster.
 4. The railway truck of claim 1 whereinthe friction shoe provides both constant and variable damping tovertical movement of the bolster in the sideframe center opening.
 5. Therailway truck of claim 4 wherein the friction shoe provides forcesacting on the bolster to assist in keeping the bolster in a transverserelationship to the sideframe.
 6. The railway truck of claim 4 whereinthe friction shoe provides forces acting on the bolster to assist inkeeping the bolster and sideframe from moving into a parallelogramrelationship.
 7. A railway car truck comprising a sideframe having asubstantially upright column partially defining a center opening, abolster having an end supported in the sideframe center opening forvertical movement therein, a vertical surface on the sideframe column,sloped surfaces on the bolster, a friction shoe comprising asubstantially vertical surface and a sloped surface extending at anacute angle with the vertical surface, a spring urging the friction shoesloped surface into engagement with the vertical surface on thesideframe column and with the sloped surface of the bolster.
 8. Therailway truck of claim 7 further comprising a first wear plate attachedto the vertical surface on the sideframe column.
 9. The railway truck ofclaim 8 wherein the horizontal spring provides a constant lateral forceurging the friction shoe vertical surface into engagement with the firstwear plate on the sideframe column.
 10. The railway truck of claim 7wherein the vertical spring provides a variable force urging thefriction shoe sloped surface into engagement with the sloped surface ofthe bolster.
 11. The railway truck of claim 7 wherein the friction shoeprovides both constant and variable damping to vertical movement of thebolster in the sideframe center opening.
 12. The railway truck of claim11 wherein the friction shoe provides forces acting on the bolster toassist in keeping the bolster in a transverse relationship to thesideframe.
 13. The railway truck of claim 11 wherein the friction shoeprovides forces acting on the bolster to assist in keeping the bolsterand sideframe from moving into a parallelogram relationship.